In general, drive mechanisms for audio tape cassettes, video tape cassettes, data tape cartridges, removable disk cartridges and other removable media must have some way to mechanically position a removable medium relative to internal drive parts that have fixed positions. For example, for typical magnetic tape cartridges and drives, a magnetic head in the drive has a fixed position in a direction perpendicular to the plane of the tape and the magnetic tape in the removable cartridge must be precisely aligned relative to the magnetic head. In addition, in general, the tape cartridge must be securely latched into the alignment position to prevent movement of the cartridge relative to the head during vibration or mechanical shock of the drive.
Of particular interest to the present application are belt-driven, rigid baseplate, magnetic tape mini-cartridges commonly used in the personal computer industry for data storage. In general, these mini-cartridges have evolved from a data cartridge design that was first introduced for use in the computer industry by the Minnesota Mining and Manufacturing Company (3M) in the early 1970's (U.S. Pat. No. 3,692,255, issued to Robert A. Von Behren in 1972). The belt driven magnetic data cartridges introduced by 3M in the early 1970's were approximately 100 mm by 150 mm and the magnetic tape was 6.35 mm (0.250 inches) wide. Cartridges of that size and corresponding drive mechanisms are still commercially available. In 1976, smaller mini-cartridges were developed, as described by Alan J. Richards, Mini Data Cartridge: A Convincing Alternative for Low-Cost, Removable Storage, Hewlett-Packard Journal, May, 1976. The mini-cartridge size is 63.5 mm by 82.5 min. Versions of the mini-cartridge are commercially available from a variety of vendors with tape widths varying from 3.81 mm (0.150 inches) to 8.00 mm (0.315 inches).
Recently, 3M has introduced improved mini-cartridges with increased data capacity. The new mini-cartridges are larger than the mini-cartridges described above. There is a need for drives that can accommodate (mechanically align and latch) both the old and new tape mini-cartridges.
FIG. 1A (prior art) illustrates a mini-cartridge 100 and compatible drive 102. The mini-cartridge 100 has a metal baseplate 104 and a plastic cover 106. The plastic cover 106 on the mini-cartridge 100 has a top surface 108 (the largest surface), a front surface 110 having two openings 112, 114) (one (112) for accepting a drive roller in the drive mechanism and a second (114) for accepting the magnetic head in the drive mechanism), and two side surfaces (116, 118). Each side surface has an elongated channel (for example, channel 120 for side 118) parallel to the metal baseplate 104 with one side of each channel formed by an exposed portion of the top of the metal baseplate.
The metal baseplate has a top surface 122 (facing the plastic cover) and a bottom surface 124. The top surface 122 of the metal baseplate 104 is partially exposed and the bottom surface 124 is fully exposed. Figure 1B (prior art) is a top view of the metal baseplate 104 with the plastic top and other parts removed. The dashed lines 126 and 128 indicate the position of the side walls of the plastic top illustrating the area of the baseplate that is exposed. A notch 119 (one of two) is explained below. Three reference points (130, 132, and 134) on the exposed portion of the top surface of the metal baseplate define a reference plane (datum) for the mini-cartridge. The mini-cartridge reference plane must be precisely aligned relative to a corresponding reference plane within the drive 102.
A typical drive for a mini-cartridge has elongated guides (FIG. 1A, 136, 138) corresponding to the channels (FIG. 1A, 116, 118) in the mini-cartridge sides for alignment of the mini-cartridge to the drive in a direction parallel to the metal baseplate of the mini-cartridge (FIG. 1A, arrows 140). Alignment of the mini-cartridge to the drive in the direction perpendicular to the metal baseplate of the mini-cartridge (FIG. 1A, arrows 142) is accomplished by forcing the three exposed reference points (FIG. 1B, 130, 132, 134) on the top surface of the metal baseplate up against three corresponding reference points on the lower surfaces of the chassis guides (FIG. 1A, 136, 138). Typically, the forces applied for alignment are also sufficient to latch the mini-cartridge into the drive, preventing cartridge-drive relative movement during vibration and mechanical shock.
FIG. 1C (prior art) illustrates a side view of the baseplate 104 in alignment with chassis guide 138. Note that reference points 132 and 134 on the baseplate 104 are in contact with corresponding reference points or surfaces 152 and 154 on the guide 138 in the drive chassis. Alignment force (arrow 150) is provided by a spring loaded roller 148 in the drive chassis that presses up onto the forward edge of notch 119 in the baseplate. Forward force results from the round roller pressing on the forward edge of the notch. An identical roller engages an identical notch on the opposite face (116) of the mini-cartridge. The vertical force provides alignment of the top surface reference points (130, 132, and 134). The forward force provides alignment of the front surface of the baseplate 104 against corresponding chassis stops 156.
The new mini-cartridges have a plastic cover front surface that is dimensionally identical to the front surface 110 of the older mini-cartridges. All other surfaces, however, are changed to accommodate larger tape reels. As a result of the larger tape reels, the channels in the mini-cartridge sides cannot extend along the entire length of the sides. As a result of shorter side channels, only a limited portion of the top surface of the metal baseplate is exposed. In particular, one of the three reference points (FIG. 1B, reference point 134) defined for the older mini-cartridges is not exposed. The new mini-cartridges could be clamped within the reduced area of exposed baseplate top surface. However, the new mini-cartridges have a substantial mass outside the exposed area of the baseplate that must be cantilevered if the clamping is only within the exposed area. Therefore, the smaller exposed area may not be sufficient to ensure adequate latching for vibration and mechanical shock. In addition, any increased clamping forces may also undesirably increase the force required to insert the mini-cartridge into the drive. New methods and mechanisms are needed to align and latch the new mini-cartridges and the new alignment and latching mechanisms must also be compatible with the older mini-cartridges.